1. Field of the Invention
The present invention relates to a liquid discharge recording head (ink jet recording head) used in liquid discharge recording (ink jet recording) for discharging liquid such as ink toward a recording medium, and a method for manufacturing such a liquid discharge recording head.
2. Related Background Art
As one aspect of recording apparatus for forming an image (here, regardless of meanings, a character, a figure, a pattern and/or the like are referred to as xe2x80x9cimagexe2x80x9d) on a recording medium such as a recording paper, there is a liquid discharge recording apparatus (ink jet recording apparatus) for discharging minute ink droplet(s) from minute discharge port(s).
Among the liquid discharge recording heads, there are a liquid discharge recording head of edge shooter type in which an ink droplet is discharged in parallel with a substrate on which energy generating elements are formed and a liquid discharge recording head of side shooter type in which an ink droplet is discharged in perpendicular to the substrate. For example, Japanese Patent Application Laid-open Nos. 4-10940 (1992), 4-10941 (1992) and 4-10942 (1992) disclose a liquid discharge recording head of side shooter type. In the liquid discharge recording heads disclosed in these documents, an ink droplet is discharged while communicating a bubble generated by heating the heat generating resistance body with the atmosphere. In such a liquid discharge recording head, reduction of a distance between the energy generating element and the orifice and small liquid droplet recording which were difficult to achieve in the liquid discharge recording head of side shooter type in the conventional manufacturing method (for example, disclosed in Japanese Patent Application Laid-open No. 62-234941 (1987) can easily be achieved, and, thus, recent request for highly fine recording can be satisfied.
Further, in recent years, a higher output speed of a printer has been requested. The reason is that high density ink droplets is requested as a processing speed of a computer has been enhanced and an ink droplet has been minimized in order to output a highly fine image. Further, in printers for handling a large size recording medium and printers connected to a network, the request for high speed becomes more noticeable. The high output speed of the printer can be achieved by increasing the number of ink droplets per unit time, i.e., ink discharging frequency and/or by increasing the number of ink discharge ports. Normally, the high output speed of the printer is achieved by increasing the both. However, when the number of ink discharge ports is increased, nozzle arrays are increased, which leads to increase the dimension of the liquid discharge recording head.
In such a liquid discharge recording head, as shown in FIG. 22A, an orifice plate 105 having a plurality of ink discharge ports 106 is joined to a substrate 102. As shown in FIG. 22B, an ink supply port 107 is formed in the substrate 102, and a plurality of energy generating elements (heat generating resistance bodies) 101 are disposed on a surface of the substrate 102 joined to the orifice plate 105 at positions corresponding to the ink discharge ports 106. As shown in FIG. 22C, an ink flow path (liquid chamber) 108 extending from the ink supply port 107 and communicated with the ink discharge ports 106 above the heat generating resistance bodies 101 is formed between the substrate 102 and the orifice plate 105. Accordingly, ink is supplied from the ink supply port 107 to the ink flow path 108 and is discharged from the ink discharge port 106 by pressure of a bubble generated by the action of the heat generating resistance body 101. Incidentally, in the drawings, for simplicity""s sake, the ink discharge ports and the heat generating resistance bodies are schematically shown only in part or plural fine discharge port arrays are shown in a straight manner.
In a method for manufacturing such a liquid discharge recording head, as shown in FIGS. 23A to 23D, a soluble resin layer 103 is formed on the substrate 102 on which the ink discharging energy generating elements (heat generating resistance bodies) 101 were formed, and, then, a coat resin layer 105 which constitutes the orifice plate later is coated by spin coating or the like. Thereafter, the soluble resin layer 103 is dissolved and the ink supply port 107 is formed in the substrate 102. As a result, the dissolved portion of the resin layer 103 becomes the ink flow path 108 communicated with the ink discharge ports 106 and the ink supply port 107, and the heat generating resistance bodies 101 are disposed in a confronting relationship to the ink flow path 108. However, in this method, as shown in FIG. 22C and by the two dot and chain line in FIG. 23, it is difficult to form the coat resin layer in a flat shape. As shown in FIGS. 23B to 23D, the coat resin layer 105 is formed along corner portions (stepped portions) of the soluble resin layer 103, with the result that a thick portion and a thin portion is included in the orifice plate 105 (dispersion). When a liquid discharge recording head in which the thickness of the orifice plate 105 is uneven is used, the thin portion of the orifice plate 105 is subjected to concentrated stress, with the result that the orifice plate may be apt to be peeled from the substrate 102, reliability may be worsened and a service life of the liquid discharge recording head may be shortened. Further, since the ink discharged amount is determined by a distance (gap) between the heat generating resistance body 101 for generating the ink discharge energy and the front surface of the orifice plate 101, as shown in FIGS. 23B to 23D, when the thickness of the orifice plate 105 is not uniform and the gaps between the orifice plate and the heat generating resistance bodies 101 are uneven, it is very difficult to stably effect the small liquid droplet recording which is an effective method for realizing the highly fine recording.
A method for solving such a problem is disclosed in Japanese Patent Application Laid-open Nos. 10-157150 (1998) and 11-138817 (1999). In the manufacturing method disclosed in such documents, for the purpose of the flattening of the orifice plate 105, the soluble resin layer 103 is formed not only as the pattern of the ink flow path 108 but also around outer periphery thereof, and the coat resin layer 105 is formed by using the soluble resin layer 103 as foundation. This manufacturing method will be fully explained with reference to FIGS. 24A to 24D. Incidentally, in the actual manufacturing, although a plurality of heads are usually manufactured simultaneously on a single substrate, for simplifying the explanation, here, the manufacture of the single head will be explained.
First of all, as shown in FIG. 24A, a soluble resin layer 103 is formed on a substrate 102 on which a predetermined number of heat generating resistance bodies (electrical/thermal converting elements) 101 as ink discharging energy generating elements were arranged at predetermined positions. In this case, the soluble resin layer 103 includes not only a pattern 103a constituting an ink flow path but also a pattern 103b constituting a foundation encircling outer periphery of the ink flow path. Incidentally, the soluble resin layer 103 is coated, for example, by laminating of dry film or spin coating of resist and then is patterned, for example, by exposure and development by using ultraviolet ray (deep-UV light).
More concretely, after polymethyl isopropenyl ketone (such as ODUR-1010 manufactured by TOKYO OUKA KOGYO Co., Ltd.) is coated by spin coating and then is dried, it is patterned exposure and development by using deep-UV light.
Then, as shown in FIG. 24B, a coat resin layer 105 is formed on the soluble resin layer 103 by spin coating or the like.
In this case, if there is no pattern 103b as the foundation, since the portion encircling the outer peripheral portion of the pattern 103a constituting the ink flow path becomes a lower surface which exposes the substrate 102 completely through a large area, as shown in FIGS. 23B to 23D, the coat resin layer 105 forms a mountain shape with an apex corresponding to the pattern 103a gradually sloping down, thereby making the thickness of the coat resin layer uneven. However, as shown in FIG. 24B, when the pattern 103b constituting the foundation is provided, also in the portion encircling the outer peripheral portion of the pattern 103a constituting the ink flow path, since a lower surface which exposes the substrate 102 is not so a large area, the coat resin layer 105 is formed with a uniform height. Of course, the coat resin layer 105 is formed very flatly above the pattern 103a constituting the ink flow path.
Then, as shown in FIG. 24C, ink discharge ports 106 are formed in the coat resin layer 105, and an opening portion 104 is formed above and around the pattern 103b constituting the foundation. Formation of the ink discharge ports 106 and the opening portion 104 can be effected by exposure and development using ultraviolet ray (deep-UV light), for example. More concretely, after negative resist is coated by spin coating and is dried, by pattern-exposing and developing it, the ink discharge ports 106 and the opening portion 104 can be formed.
Then, the substrate 102 is subjected to chemical etching to form an ink supply port 107. For example, when an Si substrate is used as the substrate, the ink supply port 107 is formed by anisotropic etching using strong alkali solution such as KOH, NaOH or TMAH. As more concrete example, the ink supply port 107 is formed by patterning a thermal oxidation film formed on an Si substrate in which crystal orientation is  less than 110 greater than  and then by etching the Si substrate by using solution including TMAH of 22% a temperature of which is adjusted to 80xc2x0 C. for ten and several hours.
Then, as shown in FIG. 24D, the soluble resin layer 103 is dissolved to form the ink flow path 108 and a groove 109 encircling the ink flow path. The removal of the soluble resin layer 103 can be performed by effecting whole surface exposure using deep-UV light and then by effecting dissolution and drying, and, when ultrasonic treatment is effected upon dissolution, the resin layer 103 can be removed positively for a shorter time.
Although not shown, a plurality of liquid discharging mechanisms shown in FIG. 24D are formed on the single substrate 102 by the aforementioned steps, and, after such mechanisms are completed, the substrate 102 is divided and cut by a dicing saw to form chips, and, after electrical connection for driving the heat generating resistance bodies is completed, a member such as an ink tank for supplying the ink is joined to the chip, thereby completing the liquid discharge recording head.
Incidentally, the formation of the ink supply port 107 may be performed before the formation of the soluble resin layer 103 and/or before the formation of the ink discharge ports 106 and the opening portion 104.
In this way, according to the method in which the groove 109 is formed around the ink flow path 108, since the coat resin layer 105 can be formed flatly and the thickness of the orifice plate 105 becomes uniform, in the liquid discharge recording head, the distance between the front surface of the orifice plate 105 and the heat generating resistance bodies 101 becomes uniform, with the result that the small liquid droplet recording for realizing highly fine recording can be performed stably.
Further, since the orifice plate 105 does not cover all of portions other than the ink discharge ports 106 and the electrical connections, it can be prevent that the substrate 102 is deformed due to stress generated by the hardening and/or temperature change of the orifice plate 105 and that the stress concentrates on edges of the orifice plate 105, i.e., wall portions of the ink flow path 108 thereby to cause peeling between the orifice plate and the substrate 102.
Further, since the orifice plate 105 covers not only the vicinity of the ink discharge ports 106 but also outside portions thereof, a large area of the surface of the substrate 102 is not exposed, with the result that the surface of the substrate 102 is not damaged when the liquid discharge recording head is actually mounted or when the head is mounted to the printer to be used.
In this way, stress acting on the wall portions of the ink flow path 108 is reduced as small as possible, and the surface of the substrate 102 is prevented from being damaged.
FIGS. 25A to 25C schematically show the liquid discharge recording head looked at from the above. In the liquid discharge recording head, a single array of the ink discharge ports 106 is disposed at each side of the ink supply port 107.
From various tests, it was found that edge portions of the groove 109 formed around the ink flow path 108 of the ink discharge recording head manufactured in this way, i.e., edges of the orifice plate 105 may be peeled as the length of the liquid discharge recording head is increased. Particularly, in comparison with an inner side where the volume of the orifice plate 105 is reduced because of the provision of the ink discharge ports 106 and the ink flow path 108, an outer portion of the orifice plate 105 has greater volume, with the result that, since the stress acting on the outer portion of the orifice plate 105 becomes greater, the possibility of generating the peeling is increased. Further, it was also found that the greater the thickness of the orifice plate 105 of the liquid discharge recording head (to increase the stress), the greater the possibility of such peeling.
FIGS. 25A to 25C are schematic views for explaining a relationship between the stress and the peeling. Particularly, in FIGS. 25B and 25C, the arrows show directions of the stress 110 acting on the edge portions of the orifice plate 105 and changed due to expansion/contraction caused by contraction and/or heat change during the curing. The stress 110 directs toward a central portion of resin when the resin is contracted and directs outwardly (directions opposite to the arrows) when the resin is expanded. Particularly, it is considered that the stress (shown by the arrows in FIGS. 25B and 25C) which directs toward the central portion of the resin generates the peeling of the orifice plate 105.
The stress 110 acts in directions perpendicular to the groove 109 (perpendicular to a tangential line of the groove when the groove 109 is curved) at edges contacted with the groove 109 of the orifice plate 105. Thus, at the edge portions of the orifice plate 105 contacted with the groove 109, forces which try to peel the edges are generated, and, since such forces direct toward the edge portions, the stress 110 acts against the edge portions as it is, with the result that the peeling apt to be occurred.
FIG. 25C is an enlarged view of a portion encircled by a circle in FIG. 25B, for explaining stress components 110 acting on both sides of the groove 109 in detail. In FIG. 25C, there is the groove 109 at the center, and the stress components 110 act on edge portions of the groove in the orifice plate 105. As mentioned above, since the stress components 110 acts in the directions perpendicular to the edge portions of the orifice plate 105, the entire stress components 110 constitute the forces which try to peel the orifice plate 105 as they are. Since the greater the area and thickness of the orifice plate 105 the greater the stress components 110, in case of an orifice plate 105 having a greater length, the peeling is more apt to occur.
As mentioned above, in recent years, the high speed recording has been requested, and, to this end, a liquid discharge recording head having a greater length rather than a liquid discharge recording head having the greater number of ink discharge ports has been requested. However, the greater the length of the liquid discharge recording head, the greater the internal stress in the coat resin layer (orifice plate) 105 in which the ink discharge ports 106 are formed. Consequently, when print endurance tests with factor of safety regarding the practical number of prints are effected, there arise an inconvenience that the orifice plate 105 is peeled from the substrate 102 around the edges contacted with the groove 109. According to circumstances, such peeling may reach the area where the ink discharge ports 106 are formed, with the result that the discharging performance is worsened and poor recording occurs if worst comes to worst. FIGS. 26A and 26B schematically show occurrence of such peeling. As shown in FIGS. 26A and 26B, it can be seen that the peeling (peeled portions 111) occurs between the substrate 102 and the orifice plate 105 around the edge portions contacted with the groove 109.
The present invention is made in consideration of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a liquid discharge recording head of side shooter type in which peeling does not occur if the head becomes longer and which has good reliability, and a method for manufacturing such a head.
The present invention provides a liquid discharge recording head comprising a substrate on which an energy generating element for generating liquid discharging energy is provided, and an orifice plate which is laminated with the substrate and in which a discharge port corresponding to the energy generating element is provided, and wherein a liquid droplet is discharged in a direction substantially perpendicular to surfaces of the substrate and the orifice plate, and further wherein a flow path is formed between the substrate and the orifice plate, and a groove encircling the flow path is formed in the orifice plate, and edge portions of the orifice plate contacted with the groove are formed as saw-shaped portions having a number of minute indentations.
The edge portion of the orifice plate contacted with the groove does not have continuously a portion perpendicular to a direction of stress acting on the edge portion.
The indentations provided on the edge portion of the orifice plate contacted with the groove may be constituted by a combination of straight segments, and each straight segment may not have the portion perpendicular to the direction of the stress acting on the edge portion. Alternatively, the indentations provided on the edge portion of the orifice plate contacted with the groove may be constituted by a combination of curved segments, and a tangential line to each curved segment may not have continuously the portion perpendicular to the direction of the stress acting on the edge portion. Alternatively, the indentations provided on the edge portion of the orifice plate contacted with the groove may be constituted by a combination of straight segments and curved segments, and each straight segment may not have the portion perpendicular to the direction of the stress acting on the edge portion and a tangential line to each curved segment may not have continuously the portion perpendicular to the direction of the stress acting on the edge portion.
A portion of the orifice plate disposed outside of the groove may be divided into plural regions.
At least a part of edge portions of the orifice plate contacted with the flow path may be formed as saw-shaped portions having a number of minute indentations. At least the part of the edge portions of the orifice plate contacted with the flow path does not have continuously a portion perpendicular to the direction of stress acting on the edge portion.
A plurality of through-holes reaching the substrate in a thickness direction may be formed in a portion of the orifice plate except for the flow path.
A plurality of recessed portions not reaching the substrate in the thickness direction may be formed in a portion of the orifice plate except for the flow path. The recessed portions may be recessed grooves.
The portion of the orifice plate disposed outside of the groove may have a thickness smaller than those of other portions.
The orifice plate may have a ceiling portion covering a space above the groove.
Further, the present invention provides a liquid discharge recording head comprising a substrate on which an energy generating element for generating liquid discharging energy is provided and an orifice plate which is laminated with the substrate and in which a discharge port corresponding to the energy generating element is provided, and wherein a liquid droplet is discharged in a direction substantially perpendicular to surfaces of the substrate and the orifice plate, and further wherein a flow path is formed between the substrate and the orifice plate, and the orifice plate has a hole array including a plurality of holes and encircling the flow path.
The present invention further provides a method for manufacturing a liquid discharge recording head comprising a substrate on which an energy generating element for generating liquid discharging energy is provided and an orifice plate which is laminated with the substrate and in which a discharge port corresponding to the energy generating element is provided, and wherein a liquid droplet is discharged in a direction substantially perpendicular to surfaces of the substrate and the orifice plate, the method comprising a step for forming a soluble resin layer including a pattern constituting the flow path and a pattern constituting a foundation having a configuration encircling the pattern constituting the flow path on a surface of the substrate on which the energy generating element is provided, a step for forming a coat resin layer constituting the orifice plate on the substrate and the soluble resin layer, and a step for forming, by dissolving the soluble resin layer, the flow path in an area where the pattern constituting the flow path was existed and a groove in an area where the pattern constituting the foundation was existed, and being characterized in that edge portions of the pattern constituting the foundation are formed as saw-shaped portions having a number of minute indentations.
A portion of the orifice plate comprised of the coat resin layer disposed outside of the area where the flow path to be formed may be divided into plural regions.
At least a part of the edge portions of the pattern constituting the flow path may be formed as a saw-shaped portion having a number of minute indentations.
A portion of the orifice plate comprised of the coat resin layer except for the area where the flow path is to be formed may be provided with a plurality of through-holes passing through a thickness direction.
A portion of the orifice plate comprised of the coat resin layer except for the area where the flow path is to be formed may be provided with a plurality of recessed portions not passing through a thickness direction.
The method may further comprises a step for reducing a thickness of a portion of the orifice plate comprised of the coat resin layer disposed outside of the area where the flow path is to be formed by half etching.
A ceiling portion for the groove may be formed by remaining at least a part of a portion covering a space above the area where the pattern constituting the foundation is to be formed on the coat resin layer constituting the orifice plate.
The present invention further provides a method for manufacturing a liquid discharge recording head comprising a substrate on which an energy generating element for generating liquid discharging energy is provided and an orifice plate which is laminated with the substrate and in which a discharge port corresponding to the energy generating element is provided, and wherein a liquid droplet is discharged in a direction substantially perpendicular to surfaces of the substrate and the orifice plate, the method comprising a step for forming a soluble resin layer including a pattern constituting the flow path and a pattern constituting a foundation having a cylinder array configuration encircling the pattern constituting the flow path on a surface of the substrate on which the energy generating element is provided, a step for forming a coat resin layer constituting the orifice plate on the substrate and the soluble resin layer, and a step for forming, by dissolving the soluble resin layer, the flow path in an area where the pattern constituting the flow path was existed and a hole array in an area where the pattern constituting the foundation was existed.
In the above-mentioned liquid discharge recording head, even when the head is used for a long term, the edge portions of the orifice plate are not peeled from the substrate at all or, even if such peeling occurs, the level of the peeling does not arise any practical problem, with the result that, since good and stable liquid discharge recording can be maintained, endurance and reliability can be enhanced.